A radio frequency (RF) power amplifier and its matching network are typically designed for operation at a fixed carrier frequency. At other carrier frequencies, the power amplifier often loses performance, including efficiency, output power, and linearity. For example, if a power amplifier loses linearity, it cannot satisfy its spectral mask requirements, and pre-distortion is often needed, which in turn is more complicated, consumes more power, and occupies more die area.
For modern wireless communication systems where the frequency range of interest is very wide, multiple power amplifiers may be needed to cover different frequency bands within the frequency range of interest. Unfortunately, using multiple power amplifiers can incur significant increases in cost, complexity, power consumption and die area. Having a single tunable power amplifier that can cover multiple frequency bands is a more attractive solution for these applications.